The voltage$-$clamp technique was an important technological advancement because...

A$)$ It allowed Hodgkin and Huxley to record the resting membrane potential of a neuron $($the squid giant axon$).$

B$)$ It allowed Hodgkin and Huxley to record $N{a}^{+}$and $K^{+}$currents across the axonal membrane at different fixed depolarizing voltages.

C$)$ It allowed Hodgkin and Huxley to record action potentials in the presence$/$absence of external $N{a}^{+}$ions.

D$)$ It allowed Hodgkin and Horowicz to test Bernstein's hypothesis on the ionic basis of resting membrane potential.

E$)$ All of the above.